期刊文献+
共找到399,526篇文章
< 1 2 250 >
每页显示 20 50 100
Reducing Peak-to-Average Power Ratio of a Turbo Coded OFDM
1
作者 Spyridon K. Chronopoulos Vasilis Christofilakis +1 位作者 Giorgos Tatsis Panos Kostarakis 《Wireless Engineering and Technology》 2012年第4期195-202,共8页
Peak to Average Power Ratio (PAPR) is defined as the instantaneous power (maximum value) to the average power ratio. PAPR is considered to be a major problem in OFDM systems. This problem can cause radical unexpected ... Peak to Average Power Ratio (PAPR) is defined as the instantaneous power (maximum value) to the average power ratio. PAPR is considered to be a major problem in OFDM systems. This problem can cause radical unexpected behavior of the signal fluctuation. This fluctuation is constituted by a large number of power states. The enormous number of these states leads to an additional complexity of ADCs and DACs. This research addresses the previous problem in OFDM systems utilizing Turbo Codes. μLaCP technique is employed for the purpose of decreasing PAPR. Moreover, our OFDM system was simulated in the presence of an AWGN channel with four types of codes (without the presence of ADCs and DACs). These were constituted of PCCC (typical and new), SCCC, and Convolutional Codes. Our Turbo Coded OFDM exhibited unchanged BER performance before and after the use of μLaCP technique. This was accomplished by modifying our previous PAPR reduction technique without sacrificing greatly its attributes. 展开更多
关键词 Orthogonal Frequency Division Multiplexing PEAK to Average power RATIO μ-Law μLaCP μLaIF Parallel CONCATENATED Convolutional Codes A POSTERIORI Probability Cyclic PREFIX Zero PADDING PEAK RATIO Bit Error Rate
下载PDF
Optimal Power Allocation Strategy for TBLAST Based 4G Systems
2
作者 Wu YIN Pei XIAO 《Engineering(科研)》 2009年第2期91-98,共8页
There is a big demand for increasing number of subscribers in the fourth generation mobile communication systems. However, the system performance is limited by multi-path propagations and lack of efficient power alloc... There is a big demand for increasing number of subscribers in the fourth generation mobile communication systems. However, the system performance is limited by multi-path propagations and lack of efficient power allocation algorithms in conventional wireless communication systems. Optimal resource allocation and interference cancellation issues are critical for the improvement of system performance such as throughput and transmission reliability. In this paper, a turbo coded bell lab space time system (TBLAST) with optimal power allocation techniques based on eigen mode, Newton and convex optimization method and carrier-interference-and-noise ratio (CINR) are proposed to improve link reliability and to increase throughput with reasonable computational complexity. The proposed scheme is evaluated by Monte-Carlo simulations and is shown to outperform the conventional power allocation scheme. 展开更多
关键词 Carrier Interference and Noise Ratio (CINR) Convolutional TURBO CODED BELL Space Time (TBLAST) EIGEN Mode (EM) Optimal power Allocation (OPL) Automatic Differentiation (AD) SYMBOLIC DERIVATIVE (S
下载PDF
Oxidation Kinetics of Aluminum Powders in a Gas Fluidized Bed Reactor in the Potential Application of Surge Arresting Materials
3
作者 Hong Shih 《Materials Sciences and Applications》 2019年第3期253-292,共40页
In this technical paper, the oxidation mechanism and kinetics of aluminum powders are discussed in great details. The potential applications of spherical aluminum powders after oxidation to be part of the surging arre... In this technical paper, the oxidation mechanism and kinetics of aluminum powders are discussed in great details. The potential applications of spherical aluminum powders after oxidation to be part of the surging arresting materials are discussed. Theoretical calculations of oxidation of spherical aluminum powders in a typical gas fluidization bed are demonstrated. Computer software written by the author is used to carry out the basic calculations of important parameters of a gas fluidization bed at different temperatures. A mathematical model of the dynamic system in a gas fluidization bed is developed and the analytical solution is obtained. The mathematical model can be used to estimate aluminum oxide thickness at a defined temperature. The mathematical model created in this study is evaluated and confirmed consistently with the experimental results on a gas fluidization bed. Detail technical discussion of the oxidation mechanism of aluminum is carried out. The mathematical deviations of the mathematical modeling have demonstrated in great details. This mathematical model developed in this study and validated with experimental results can bring a great value for the quantitative analysis of a gas fluidization bed in general from a theoretical point of view. It can be applied for the oxidation not only for aluminum spherical powders, but also for other spherical metal powders. The mathematical model developed can further enhance the applications of gas fluidization technology. In addition to the development of mathematical modeling of a gas fluidization bed reactor, the formation of oxide film through diffusion on both planar and spherical aluminum surfaces is analyzed through a thorough mathematical deviation using diffusion theory and Laplace transformation. The dominant defects and their impact to oxidation of aluminum are also discussed in detail. The well-controlled oxidation film on spherical metal powders such as aluminum and other metal spherical powders can potentially become an important part of switch devices of surge arresting materials, in general. 展开更多
关键词 Aluminum Spherical power GAS FLUIDIZATION Bed Oxidation Mechanism Oxide Growth Rate Gibbs Free Energy Ellingham Diagram Mathematical Modeling Dynamic System Plasma DIFFUSION DIFFUSION Coefficient Crystallographic Defect Vacancy Pressure Temperature Flow Laplace Transform Equation Boundary Condition Ficks Second Law Software Experimental Theoretical SURGE ARRESTING MATERIALS Analytical Solution
下载PDF
Comparative Study of Radiological Changes in Hands and Feet in Patients Suffering from Early Rheumatoid Arthritis by Power Doppler Ultrasound and Direct Digital Radiography
4
作者 Gargy Mondal Biswadip Ghosh +1 位作者 Manoranjan Ghosh Pampa Halder 《Open Journal of Rheumatology and Autoimmune Diseases》 2014年第1期39-42,共4页
Rheumatoid arthritis is a chronic multisystem disease of unknown cause. The characteristic feature of RA is persistent inflammatory synovitis. The natural history of disease is such that the early months of the diseas... Rheumatoid arthritis is a chronic multisystem disease of unknown cause. The characteristic feature of RA is persistent inflammatory synovitis. The natural history of disease is such that the early months of the disease are critical period during which reversible joint damage occurs. So early diagnosis of RA and appropriate drug application is the only way to save a patient from this crippling disease. In India, the cost of investigations is a significant factor for most of the patients. Ultrasonography or Power Doppler Ultra Sound (PDUS) has the advantage of being economic in spite of its sensitivity in assessing both inflammatory and destructive changes. The aim of the present study was to evaluate the diagnostic efficiency of PDUS in early rheumatoid arthritis. The study was performed with the patients attending Rheumatology Clinic. A total number of 106 patients of clinically suspected rheumatoid arthritis were studied as per selection criteria. Radiological examinations of hands were done by digital radiography and PDUS in a group of 53 patients, assessment of foot changes by PDUS and Digital Radiography were done in another similar group of 53 patients. Final diagnosis by ACR EULAR-2010 criteria is done for all the patients. The comparative study reveals that synovial vascularity as demonstrated by PDUS is much more effective in diagnosing early rheumatoid arthritis, both in hand and in feet than digital radiograph. PDUS of feet may yield earlier and better findings than hands, which is conventionally used in patients suffering from early rheumatoid arthritis. 展开更多
关键词 R.A.Rheumatoid Arthritis PDUS—power Doppler Ultrasound D.R.Digital Radiography ACR-EULARAmerican College of RHEUMATOLOGY (ACR) and the European LEAGUE against RHEUMATISM (EULAR) RFRheumatoid Factor CRPc-Reactive Protein MRIMagnetic Resonance Imaging
下载PDF
Acarine ectoparasites of Panti Forest Reserve in Johore,Malaysia 被引量:1
5
作者 Mariana A Mohd Kulaimi B +4 位作者 Halimaton I Suhaili ZA Shahrul-Anuar MS Nor Zalipah M Ho TM 《Asian Pacific Journal of Tropical Biomedicine》 SCIE CAS 2011年第1期1-5,共5页
Objective:To identify the presence of acarine ectoparasites and determine whether there is any potential public health risk in Panti Forest Reserve,Johore,Malaysia.Methods:Trapping of animals and avifauna was conducte... Objective:To identify the presence of acarine ectoparasites and determine whether there is any potential public health risk in Panti Forest Reserve,Johore,Malaysia.Methods:Trapping of animals and avifauna was conducted simultaneously along 5 expedition trails using 150 wire traps,10 harp traps and 30 mist nets for 6 consecutive nights.A total of 140 animals consisting of 7 species of birds,19 species of bats,6 species of rodents and 1 species of tree-shrew as well as 8 myriapods were examined.Results:Infestation rates of ticks,mesostigmatid mites and chiggers on animals examined were 24.3%,28.6%and 27.9%,respectively.Infestation on bats was low(1.5%) and none occurred on birds.Majority of ticks extracted were at immature stages(78.9%). Genera of ticks on animals were Amblyomma,Dermacentor,Haemaphysalis and Ixodes.Ixodes granulatus was the only species of licks identified from the animals.Examination of ticks under vegetation revealed 54%adults leading to identification of 3 species of ticks.A total of 7 species of mesostigmatid mites were found.6 species were on rodent,Maxomys mrifer and another one species,Laelaps nuttalli was found only on Leopoldamys sabanus.Laelaps sanguisugus was the only mesostigmatid found infesting tree-shrews.Seven genera of chiggers were identified.From this,5 genera were on rodents,4 genera on tree-shrews and 1 genus on a bat.Conclusions:A total of 16 genera,2 sub-genus and 14 species of acarine ectoparasites were found in this area. Findings of the survey demonstrate the presence of three spesies of acarine ectoparasites which have potential health risk i.e.Ixodes granulalus,Laelaps nuttalli and Leptotrombidium deliense. 展开更多
关键词 Acarine ECTOPARASITES Panti Forest reserve MALAYSIA Public health risk INFESTATION rate TICK Mesostigmatid mite Chigger IXODES granulatus Laelaps nuttalli Leptotrombidium deliense AVIFAUNA Rodent
下载PDF
德国历史学派与19世纪经济学方法论之争的启示 被引量:17
6
作者 何蓉 《社会》 北大核心 2005年第3期167-186,共20页
In the mid-19th century, out of their dissatisfaction with the neglect of the economic theories about other countries’ experiences in the British classic economics, the economists in the German Historical School wo... In the mid-19th century, out of their dissatisfaction with the neglect of the economic theories about other countries’ experiences in the British classic economics, the economists in the German Historical School worked hard to construct an economic theory that was congruent to the developmental stage in their own country’s culture and history. Their deeply-cherished concern about the reality in a transitional era when Germany was approaching modernization drove them to propose that the living condition of the working class be improved by the power of the state. In the late 80’s of the same century, the Methodenstreit of German Historical School versus the Austrian School broke out, after which the mainstream economics was well on its way in terms of theoretical refinement and scrutiny, whereas the influence from the Historical School gradually subsided. Even so, the lessons from the Historical School are still enlightening to research in contemporary social sciences. This paper describes the unique basics in the theory building of the Historical School; explains the background and meaning of its academic origin, research methodology, and the Methodenstreit; and from there, discusses implications for contemporary social sciences. 展开更多
关键词 19 School ACADEMIC culture science about from origin that other and power after which STILL there with hard when LATE well This its of to way are for In be on so
下载PDF
Design and Analysis of a Power Efficient Linearly Tunable Cross-Coupled Transconductor Having Separate Bias Control
7
作者 Vijaya Bhadauria Krishna Kant Swapna Banerjee 《Circuits and Systems》 2012年第1期99-106,共8页
A common current source, generally used to bias cross-coupled differential amplifiers in a transconductor, controls third harmonic distortion (HD3) poorly. Separate current sources are shown to provide better control ... A common current source, generally used to bias cross-coupled differential amplifiers in a transconductor, controls third harmonic distortion (HD3) poorly. Separate current sources are shown to provide better control on HD3) . In this paper, a detailed design and analysis is presented for a transconductor made using this biasing technique. The transconductor, in addition, is made to offer high Gm, low power dissipation and is designed for linearly tunable Gm with current mode load as one of the applications. The circuit exhibits HD3) of less than –43.7 dB, high current efficiency of 1.18 V-1 and Gm of 390 μS at 1 VGp-p @ 50 MHz. UMC 0.18 μm CMOS process technology is used for simulation at supply voltage of 1.8 V. 展开更多
关键词 ANALOG electronics low power ANALOG CMOS Circuit Operational TRANSCONDUCTANCE Amplifier (OTA) Multiple-output OTA (MOTA) MOS TRANSCONDUCTORS LINEARLY TUNABLE Gm Current efficiency Linearization Techniques Harmonic Distortion Analysis
下载PDF
A Decision Support System for Selection of Solar Power Plant Locations by Applying Fuzzy AHP and TOPSIS: An Empirical Study 被引量:3
8
作者 Athakorn Kengpol Piya Rontlaong Markku Tuominen 《Journal of Software Engineering and Applications》 2013年第9期470-481,共12页
The objective of this research is to propose a decision support system for avoiding flood on solar power plant site selection. Methodologically, the geographic information system (GIS) is used to determine the optimum... The objective of this research is to propose a decision support system for avoiding flood on solar power plant site selection. Methodologically, the geographic information system (GIS) is used to determine the optimum site for a solar power plant. It is intended to integrate the qualitative and quantitative variables based upon the adoption of the Fuzzy Analytic Hierarchy Process (Fuzzy AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) model. These methods are employed to unite the environmental aspects and social needs for electrical power systematically. Regarding a case study of the choice of a solar power plant site in Thailand, it demonstrates that the quantitative and qualitative criteria should be realized prior to analysis in the Fuzzy AHP-TOPSIS model. The fuzzy AHP is employed to determine the weights of qualitative and quantitative criteria that can affect the selection process. The adoption of the fuzzy AHP is aimed to model the linguistic unclear, ambiguous, and incomplete knowledge. Additionally, TOPSIS, which is a ranking multi-criteria decision making method, is employed to rank the alternative sites based upon overall efficiency. The contribution of this paper lies in the evolution of a new approach that is flexible and practical to the decision maker, in providing the guidelines for the solar power plant site choices under stakeholder needs: at the same time, the desirable functions are achieved, in avoiding flood, reducing cost, time and causing less environmental impact. The new approach is assessed in the empirical study during major flooding in Thailand during the fourth quarter of 2011 to 2012. The result analysis and sensitivity analysis are also presented. 展开更多
关键词 Solar power Plant Site SELECTION Decision Support System Fuzzy ANALYTIC Hierarchy Process (FAHP) Technique for Order PREFERENCE by Similarity to IDEAL Solution (TOPSIS)
下载PDF
Theory of Electromagnetism and Gravity —Modeling Earth as a Rotating Solenoid Coil
9
作者 Greg Poole 《Journal of High Energy Physics, Gravitation and Cosmology》 2017年第4期663-692,共30页
Presented in this manuscript are conventional electrical engineering tools to model the earth as a rotating electrical machine. Calculations using known parameters of the earth and measured field data has resulted in ... Presented in this manuscript are conventional electrical engineering tools to model the earth as a rotating electrical machine. Calculations using known parameters of the earth and measured field data has resulted in new understanding of the earth’s electrical system and gyroscopic rotation. The material makeup of the inner earth is better understood based on derived permeability and permittivity constants. The planet has been modeled as simple coils and then as a parallel impedance circuit which has led to fundamental insight into planetary speed control and RLC combination for Schumann Resonance of 7.83 Hz. Torque and Voltage Constants and the inverse Speed Constant are calculated using three methods and all compare favorably with Newton’s Gravitational Constant. A helical resonator is referenced and Schumann’s Resonant ideal frequency is calculated and compared with others idealism. A new theory of gravity based on particle velocity selector at the poles is postulated. Two equations are presented as the needed links between Faraday’s electromagnetism and Newtonian physics. Acceleration and Deceleration of earth is explained as a centripetal governor. A new equation for planetary attraction and the attraction of atomic matter is theorized. Rotation of the earth’s electrical coil is explained in terms of the Richardson effect. Electric power transfer from the sun to the planets is proposed via Flux Transfer Events. The impact of this evolving science of electromagnetic modeling of planets will be magnified as the theory is proven, and found to be useful for future generations of engineers and scientists who seek to discover our world and other planets. 展开更多
关键词 Ampere Biot-Savart CENTRIPETAL Acceleration CENTRIPETAL GOVERNOR Dynamo EARTH Einstein-de Haas Effect Electric Field Electromagnetism Flux Transfer Events GOVERNOR Control GRAVITY Gravitational CONSTANT Helical Resonator Lenz Law Lorentz Lightning Magnetic Field Motor CONSTANT Parallel Impedance Planet SPEED Control Schumann Resonance Richardson Effect Solenoid SPEED CONSTANT Solar power System Torque CONSTANT Velocity Selector Voltage CONSTANT
下载PDF
Applications of Mogulskii, and Kurtz-Feng Large Deviation Results to Risk Reserve Processes with Aggregate Claims
10
作者 Jorge Garcia Ana Meda 《Applied Mathematics》 2012年第12期2109-2117,共9页
In this paper we examine the large deviations principle (LDP) for sequences of classic Cramér-Lundberg risk processes under suitable time and scale modifications, and also for a wide class of claim distributions ... In this paper we examine the large deviations principle (LDP) for sequences of classic Cramér-Lundberg risk processes under suitable time and scale modifications, and also for a wide class of claim distributions including (the non-super- exponential) exponential claims. We prove two large deviations principles: first, we obtain the LDP for risk processes on D∈[0,1] with the Skorohod topology. In this case, we provide an explicit form for the rate function, in which the safety loading condition appears naturally. The second theorem allows us to obtain the LDP for Aggregate Claims processes on D∈[0,∞) with a different time-scale modification. As an application of the first result we estimate the ruin probability, and for the second result we work explicit calculations for the case of exponential claims. 展开更多
关键词 Large Deviations Cramer-Lundberg reserve Risk PROCESSES Probability Theory and Mathematical Statistics in INSURANCE Stochastic Models for CLAIM Frequency CLAIM Size and Aggregate CLAIMS reserveS
下载PDF
Dynamic Economic Dispatch for Wind Power System Considering System Security and Spinning Reserve 被引量:1
11
作者 Wangchao Dong Jing Zhang +1 位作者 Jiejie Huang Shenghu Li 《Journal of Power and Energy Engineering》 2015年第4期342-347,共6页
In this paper, dynamic economic dispatch model is proposed for power systems with bulk wind power integration. The wind turbine generators are assumed to partially undertake the spinning reserve for the thermal genera... In this paper, dynamic economic dispatch model is proposed for power systems with bulk wind power integration. The wind turbine generators are assumed to partially undertake the spinning reserve for the thermal generator. A double-layer optimization model is proposed. The outer layer use the differential evolution to search for the power output of thermal generators, and the inner layer use the primal-dual interior point method to solve the OPF of the established output state. Finally, the impact of spinning reserve with wind power on power system operating is validated. 展开更多
关键词 SPINNING reserve Wind power Dynamic ECONOMIC DISPATCH (DED) Differential Evolution METHOD INTERIOR Point METHOD
下载PDF
Measurement of two new indicators of cardiac reserve in humans, rats, rabbits, and dogs
12
作者 Yanxia Zhao Dingguo Xu +5 位作者 Shouzhong Xiao Xiaobo Yan Jianming Liu Yong Liu Linmei Luo Guoxiang Xia 《Journal of Biomedical Science and Engineering》 2013年第10期960-963,共4页
Background: It is difficult to observe the phenomena of cardiac fatigue under a low or moderate workload test, and little was reported about cardiac fatigue under a heavy workload test because of the potential risk (s... Background: It is difficult to observe the phenomena of cardiac fatigue under a low or moderate workload test, and little was reported about cardiac fatigue under a heavy workload test because of the potential risk (sudden death) of prolonged strenuous exercise. Animal experiments would be helpful to resolve this problem. The objective of this study was to obtain baseline data of two new indicators of cardiac reserve in rats, rabbits, and dogs. Methods: Ten New Zealand White rabbits (1. 5 to 2 kg, 4 females), 10 male Wistar rats (2 months old), and 10 Golden Retriever dogs (40 days old, 5 females) were included in this study. Phonocardiogram of each animal was recorded. The basic points concerning heart sound quantitative analysis were: 1) measuring the duration and the amplitude of relevant heart sound components;2) calculating and analyzing relevant indicators based on the data obtained from the above measurements, including the ratio of diastolic to systolic duration (D/S) and the ratio of the amplitude of the first heart sound to the amplitude of the second heart sound (S1/S2). Results: The baseline data of D/S ratio and S1/S2 ratio in rats, rabbits, and dogs were obtained. The swimming time to exhaustion for rabbits was several to a dozen minutes, and for rats, several hours. Conclusion: D/S ratio has an important biological implication, which is a safe and easy indicator for evaluating the cardiac health status of both animals and humans. 展开更多
关键词 RATIO of DIASTOLIC to Systolic Duration (D/S) The RATIO of the AMPLITUDE of the First HEART SOUND to the AMPLITUDE of the Second HEART SOUND (S1/S2) CARDIAC reserve CARDIAC Fatigue Biological Implication HEART Rate (HR)
下载PDF
PSS and SVC Controller Design using Chaos, PSO and SFL Algorithms to Enhancing the Power System Stability
13
作者 Saeid Jalilzadeh Reza Noroozian +1 位作者 Mahdi Sabouri Saeid Behzadpoor 《Energy and Power Engineering》 2011年第2期87-95,共9页
In this paper, the Authors present the designing of power system stabilizer (PSS) and static var compensator (SVC) based on chaos, particle swarm optimization (PSO) and shuffled frog leaping (SFL) Algorithms has been ... In this paper, the Authors present the designing of power system stabilizer (PSS) and static var compensator (SVC) based on chaos, particle swarm optimization (PSO) and shuffled frog leaping (SFL) Algorithms has been presented to improve the power system stability. Single machine infinite bus (SMIB) system with SVC located at the terminal of generator has been considered to evaluate the proposed SVC and PSS controllers. The coefficients of PSS and SVC controller have been optimized by Chaos, PSO and SFL algorithms. Fi-nally the system with proposed controllers is simulated for the special disturbance in input power of genera-tor, and then the dynamic responses of generator have been presented. The simulation results show that the system composed with recommended controller has outstanding operation in fast damping of oscillations of power system and describes an application of Chaos, PSO and SFL algorithms to the problem of designing a Lead-Lag controller used in PSS and SVC in power system. 展开更多
关键词 power System STABILIZER (PSS) Static Var Compensator (SVC) Single Machine Infinite Bus (SMIB) CHAOS Shuffled FROG Leaping (SFL) Particle Swarm Optimization (PSO)
下载PDF
商品房住宅区公共物业自治管理制度分析 以上海市水仙苑小区为例 被引量:10
14
作者 顾玫 《社会》 北大核心 2005年第4期39-69,共31页
The reform of the housing system in Shanghai has unexpectedly given rise to a self-governed property owners’ collective supervisory system, primarily in the form of Property Owners’ Supervisory Council (POSC), which... The reform of the housing system in Shanghai has unexpectedly given rise to a self-governed property owners’ collective supervisory system, primarily in the form of Property Owners’ Supervisory Council (POSC), which has picked up some of the government’s administrative functions. Although this new, institutionalized management model has theoretically made democratic managerial participation at the grassroots level possible, it has brought about endless problems, overt and covert, shortly after its appearance, some of which are even alarming. A comprehensive analysis of the data collected over a long period of time has led to the conclusion that this system is a failure, attributable to the overt factor related to skills in reality and the covert “priori” factor that is masked by the former. The existence of such “priori” factor once again demonstrates the deep-rooted, traditional managerial logic: Positive operations is society need only to depend upon individuals’ unstable self-disciplined morality rather than to build a system. The current paper points out that any change in the socioeconomic structure that has long been subject to the power of politics is to inevitably incur a corresponding global structural accommodation, including politics itself. To respond to the two factors for the failure, system building in the two overlapping areas is a must. 展开更多
关键词 system possible which that RATHER global some this has model about after power The RISE form data over time SUCH NEED only than and two to of
下载PDF
Stochastic Modeling and Power Control of Time-Varying Wireless Communication Networks
15
作者 Mohammed M. Olama Seddik M. Djouadi Charalambos D. Charalambous 《Communications and Network》 2014年第3期155-164,共10页
Wireless networks are characterized by nodes mobility, which makes the propagation environment time-varying and subject to fading. As a consequence, the statistical characteristics of the received signal vary continuo... Wireless networks are characterized by nodes mobility, which makes the propagation environment time-varying and subject to fading. As a consequence, the statistical characteristics of the received signal vary continuously, giving rise to a Doppler power spectral density (DPSD) that varies from one observation instant to the next. This paper is concerned with dynamical modeling of time-varying wireless fading channels, their estimation and parameter identification, and optimal power control from received signal measurement data. The wireless channel is characterized using a stochastic state-space form and derived by approximating the time-varying DPSD of the channel. The expected maximization and Kalman filter are employed to recursively identify and estimate the channel parameters and states, respectively, from online received signal strength measured data. Moreover, we investigate a centralized optimal power control algorithm based on predictable strategies and employing the estimated channel parameters and states. The proposed models together with the estimation and power control algorithms are tested using experimental measurement data and the results are presented. 展开更多
关键词 WIRELESS Networks TIME-VARYING WIRELESS Fading Channel Impulse Response Doppler power Spectral Density STOCHASTIC STATE-SPACE Model STOCHASTIC Modeling Optimal power Control EXPECTATION Maximization Kalman Filter
下载PDF
Power Maximization and Control of Variable-Speed Wind Turbine System Using Extremum Seeking
16
作者 Safanah M. Rafaat Rajaa Hussein 《Journal of Power and Energy Engineering》 2018年第1期51-69,共19页
Maximizing the power capture is an important issue to the turbines that are installed in low wind speed area. In this paper, we focused on the modeling and control of variable speed wind turbine that is composed of tw... Maximizing the power capture is an important issue to the turbines that are installed in low wind speed area. In this paper, we focused on the modeling and control of variable speed wind turbine that is composed of two-mass drive train, a Squirrel Cage Induction Generator (SCIG), and voltage source converter control by Space Vector Pulse Width Modulation (SPVWM). To achieve Maximum Power Point Tracking (MPPT), the reference speed to the generator is searched via Extremum Seeking Control (ESC). ESC was designed for wind turbine region II operation based on dither-modulation scheme. ESC is a model-free method that has the ability to increase the captured power in real time under turbulent wind without any requirement for wind measurements. The controller is designed in two loops. In the outer loop, ESC is used to set a desired reference speed to PI controller to regulate the speed of the generator and extract the maximum electrical power. The inner control loop is based on Indirect Field Orientation Control (IFOC) to decouple the currents. Finally, Particle Swarm Optimization (PSO) is used to obtain the optimal PI parameters. Simulation and control of the system have been accomplished using MATLAB/Simulink 2014. 展开更多
关键词 Wind Turbine Indirect Field Orientation CONTROL (IFOC) Maximum power Point Tracking (MPPT) Extremum SEEKING CONTROL (ESC) Particle SWARM Op-timization (PSO) PI Controller
下载PDF
IBM虚拟和Power5技术帮助CIF提升竞争优势
17
《中国金融电脑》 2005年第7期94-94,共1页
近日,法国知名金融机构之一的法国房地产信贷公司(CIF)选择IBM作为其战略系统技术提供商。此前,CIF一直寻求改善各地客户服务并部署全新政府规章制度。基于此,CIF选择领先的IBM随需应变虚拟技术、IBM eServeri 570服务器以及IBM Tota... 近日,法国知名金融机构之一的法国房地产信贷公司(CIF)选择IBM作为其战略系统技术提供商。此前,CIF一直寻求改善各地客户服务并部署全新政府规章制度。基于此,CIF选择领先的IBM随需应变虚拟技术、IBM eServeri 570服务器以及IBM TotalStorage DS8000存储系统来实现IT基础架构简化,并取代现有产品。CIF公司将5台服务器和多种异构存储系统整合到一台IBM eServer i570服务器和一台IBM TotalStorage DS8000存储系统中。这种设计的目的是为CIF公司300个营业网点和2400多位员工提供强有力的支持。 展开更多
关键词 IBM CIF power5 TOTALSTORAGE ESERVER
下载PDF
Wind Power Potential in Interior Alaska from a Micrometeorological Perspective 被引量:1
18
作者 Hannah K.Ross John Cooney +5 位作者 Megan Hinzman Samuel Smock Gary Sellhorst Ralph Dlugi Nicole Molders Gerhard Kramm 《Atmospheric and Climate Sciences》 2014年第1期100-121,共22页
The wind power potential in Interior Alaska is evaluated from a micrometeorological perspective. Based on the local balance equation of momentum and the equation of continuity we derive the local balance equation of k... The wind power potential in Interior Alaska is evaluated from a micrometeorological perspective. Based on the local balance equation of momentum and the equation of continuity we derive the local balance equation of kinetic energy for macroscopic and turbulent systems, and in a further step, Bernoulli’s equation and integral equations that customarily serve as the key equations in momentum theory and blade-element analysis, where the Lanchester-Betz-Joukowsky limit, Glauert’s optimum actuator disk, and the results of the blade-element analysis by Okulov and Sorensen are exemplarily illustrated. The wind power potential at three different sites in Interior Alaska (Delta Junction, Eva Creek, and Poker Flat) is assessed by considering the results of wind field predictions for the winter period from October 1, 2008, to April 1, 2009 provided by the Weather Research and Forecasting (WRF) model to avoid time-consuming and expensive tall-tower observations in Interior Alaska which is characterized by a relatively low degree of infrastructure outside of the city of Fairbanks. To predict the average power output we use the Weibull distributions derived from the predicted wind fields for these three different sites and the power curves of five different propeller-type wind turbines with rated powers ranging from 2 MW to 2.5 MW. These power curves are represented by general logistic functions. The predicted power capacity for the Eva Creek site is compared with that of the Eva Creek wind farm established in 2012. The results of our predictions for the winter period 2008/2009 are nearly 20 percent lower than those of the Eva Creek wind farm for the period from January to September 2013. 展开更多
关键词 Wind power power Efficiency Wind power Potential Wind power Prediction WRF/Chem MICROMETEOROLOGY Momentum Theory Blade Element Analysis Betz Limit Glauerts Optimum Rotor Balance Equation for Momentum Equation of Continuity Balance Equation for Kinetic Energy ReynoldsAverage Hesselbergs Average Bernoullis Equation Integral Equations Weibull Distribution General Logistic Function Eva Creek Wind Farm
下载PDF
Predicting of Power Quality Steady State Index Based on Chaotic Theory Using Least Squares Support Vector Machine 被引量:2
19
作者 Aiqiang Pan Jian Zhou +2 位作者 Peng Zhang Shunfu Lin Jikai Tang 《Energy and Power Engineering》 2017年第4期713-724,共12页
An effective power quality prediction for regional power grid can provide valuable references and contribute to the discovering and solving of power quality problems. So a predicting model for power quality steady sta... An effective power quality prediction for regional power grid can provide valuable references and contribute to the discovering and solving of power quality problems. So a predicting model for power quality steady state index based on chaotic theory and least squares support vector machine (LSSVM) is proposed in this paper. At first, the phase space reconstruction of original power quality data is performed to form a new data space containing the attractor. The new data space is used as training samples for the LSSVM. Then in order to predict power quality steady state index accurately, the particle swarm algorithm is adopted to optimize parameters of the LSSVM model. According to the simulation results based on power quality data measured in a certain distribution network, the model applies to several indexes with higher forecasting accuracy and strong practicability. 展开更多
关键词 CHAOTIC THEORY Least SQUARES Support Vector Machine (LSSVM) power Quality STEADY State Index Phase Space Reconstruction Particle SWARM Optimization
下载PDF
Implementation of Dynamic Line Rating in a Sub-Transmission System for Wind Power Integration
20
作者 Saifal Talpur Carl Johan Wallnerstrom +1 位作者 Patrik Hilber Christer Flood 《Smart Grid and Renewable Energy》 2015年第8期233-249,共17页
Based on conventional static line rating method, the actual current carrying capability of overhead conductors cannot be judged. Due to continuous increment in electricity demand and the difficulties associated with n... Based on conventional static line rating method, the actual current carrying capability of overhead conductors cannot be judged. Due to continuous increment in electricity demand and the difficulties associated with new line constructions, the overhead lines are therefore required to be rated based on a method that should establish their real-time capability in terms of electricity transmission. The method used to determine the real-time ampacity of overhead conductors not only can enhance their transmission capacity but can also help in allowing excessive renewable generation in the electricity network. In this research work, the issues related to analyzing an impact of wind power on periodical loading of overhead line as well as finding its static and dynamic ampacities with line current are investigated in detail. Moreover, the investigation related to finding a suitable location for the construction of a 60 MW wind farm is taken on board. Thereafter, the wind park is integrated with a regional grid, owned by Fortum Distribution AB. In addition to that, the electricity generated from the wind park is also calculated in this project. Later on, the work is devoted to finding the static and dynamic line ratings for “VL3” overhead conductor by using IEEE-738-2006 standard. Furthermore, the project also deals with finding the line current and making its comparison with maximum capacity of overhead conductor (VL3) for loading it in such a way that no any violation of safe ground clearance requirements is observed at all. Besides, the line current, knowing the conductor temperature when it transmits the required electricity in the presence of wind power generation is also an important factor to be taken into consideration. Therefore, based on real-time ambient conditions with actual line loading and with the help of IEEE-738-2006 standard, the conductor temperature is also calculated in this project. At the end, an economic analysis is performed to evaluate the financial advantages related to applying the dynamic line ratings approach in place of traditional static line ratings technique across an overhead conductor (VL3) and to know how much beneficial it is to temporarily postpone the rebuilding and/or construction of a new transmission line. Furthermore, an economic analysis related to wind power system is taken into consideration as well to get familiar with the costs related to building and connecting a 60 MW wind farm with the regional grid. 展开更多
关键词 Overhead Conductor STATIC and DYNAMIC Ampacities Real-Time Weather Conditions STATIC and DYNAMIC LINE RATING Techniques WIND power Integration Regional Grid LINE Current. Conductor Temperature WIND power ECONOMICS DYNAMIC LINE RATING ECONOMICS
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部